The Digital Video Broadcasting-Terrestrial standard (DVB-T) utilises Orthogonal Frequency Division Multiplexing (OFDM) to communicate data representing video images and sound to receivers via a broadcast radio communications signal. There are known to be two modes for the DVB-T standard which are known as the 2 k and the 8 k mode. The 2 k mode provides 2048 sub-carriers whereas the 8 k mode provides 8192 sub-carriers.
In order to improve the integrity of data communicated by either the 2 k mode or the 8 k mode a symbol interleaver is provided in order to interleave input data symbols as these symbols are mapped onto the carrier signals of an OFDM symbol. Such a symbol interleaver comprises an interleaver memory in combination with an address generator. The address generator generates an address for each of the input symbols, each address indicating one of the carrier signals of the OFDM symbol onto which the data symbol is to be mapped. For the 2 k mode and the 8 k mode an arrangement has been disclosed in the DVB-T standard for generating the addresses for the mapping. The address generator is known to comprise a linear feed back shift register which is operable to generate a pseudo random bit sequence and a permutation circuit. The permutation circuit permutes the order of the content of the linear feed back shift register in order to generate an address. The address provides an indication of one of the OFDM carriers for carrying an input data symbol stored in the interleaver memory, in order to map the input symbols onto the carrier signals of the OFDM symbol.
As well as the 2 k mode and the 8 k mode it has also been proposed to provide a 4 k mode. The 4 k mode has been used in the Japanese standard for digital broadcast television, which is the Integrated Service Digital Broadcasting (ISDB) system.